北京PM_1中的化学组成及其控制对策思考

Aerosol Chemical Compositions of Beijing PM_1 and Its Control Countermeasures

通过分析北京城区2007年夏季和秋季、2008年冬季和春季4个季节PM_1中硫酸盐、硝酸盐、铵盐、有机物和黑碳等气溶胶化学组成,结合对我国及全球主要区域PM_(10)中上述气溶胶组分及矿物气溶胶组成的评估,发现因受干旱区产生的沙尘和城市逸散性粉尘的共同影响,整个亚洲大陆,尤其是我国的矿物气溶胶浓度与欧美国家城市区域气溶胶总和的平均值相当或更高。我国在重视控制PM_(2.5)等细粒子污染的同时,不应忽视对PM_(2.5)～PM_(10)之间粗粒子的控制力度;北京城区春、夏、秋、冬的PM_1平均质量浓度分别约为94,74,66μg·m^(-3)和91μg·m^(-3),全年平均约为81μg·m^(-3),其中有机物气溶胶约占41%,硫酸盐占16%,硝酸盐占13%,铵盐占8%,黑碳和氯化物分别占11%和3%,细矿物气溶胶约贡献7%。对于PM_(2.5)污染的控制,关键是消减PM_1中主要气溶胶粒子的排放与转化,其中对有机物的控制更为重要,尽管对于北京而言进一步污染控制的难度已经很大。从科学上来说,即使我国的控制措施能百分之百实现,也很难稳定地达到欧美国家的空气质量水平,因为我国本底矿物气溶胶的浓度较高。应进一步评估各项控制措施的适用性,并制定考虑我国人群健康状况的PM_(2.5)空气质量标准。

The mass concentrations of sulfate,nitrate,ammonium products,organic matter and black carbon are measured at urban Beijing during summer,autumn of 2007 and winter,spring of 2008.Combining assessment of major chemical compositions in less than 10 micron particles with at least an entire year data from various rural and urban sites in 16 areas of the world,the concentration level of mineral aerosol in China, which is partially a result of sand and dust transported from desert areas and contributions from urban fugitive dust/fly ash sources,is found to be almost equivalent to or even higher than the sum of all kind of aerosols in urban Europe and North America,suggesting the control countermeasures for aerosol particle in diameter between 2.5 and 10 micron in China should not be neglected,especially when the country pays much attention to control the fine PM2.5 particles.In urban Beijing,the averaged concentrations of PM1 are around 94,74,66μg ？ m-3 and 91μg ？ m-3 for spring,summer,autumn and winter,respectively,with the annual mean of 81μg ？ m-3.The relative contributions of organics,sulfate,nitrate and ammonium product are about 41%,16%,13%and 8%,respectively.The black carbon and chloride contribute Beijing PM1 about 11%and 3%,respectively.The fine mineral aerosol contributes about 7%.The key of control PM2.5 is to reduce the main emission species and their chemical transformation of PM1 particles, and the more important is to control the organic matter at Beijing,although Beijing’s pollution control has been very difficult since 26 million people living there.To be scientifically,even if China’s control countermeasures can achieve one hundred percent,it is also hard to reach the air quality level of Europe and North America,because of the higher background mineral aerosol level.The cost-effective control measures and new PM2.5 standard considering the health of Chinese need to be further investigated.